The present invention relates to technique of measuring a quantity of air inducted into a cylinder section of an engine in accordance with a quantity of air inside an intake manifold determined by a balance calculation between an inflowing air quantity and an outflowing air quantity. In particular, the present invention relates to such engine cylinder induction air quantity measurement adapted to an engine provided with a valve overlap.
U.S. Pat. No. 6,328,007B1 (corresponding to Published Japanese Patent application Kokai No. 2001-50091) shows a process of balance calculation between the inflowing and outflowing air quantities to determine an intake manifold inside air quantity, and to calculate an engine cylinder induction air quantity in accordance with the manifold inside air quantity and a cylinder volume.
The balance calculation process is not sufficiently adequate when an engine is stopped at a crank position within a valve overlap since air is drawn into the intake manifold from the exhaust system.
It is an object of the present invention to provide apparatus and/or method of measuring an engine cylinder induction air quantity more accurately even if an engine is stopped at a position within the valve overlap.
According to the present invention, an engine cylinder induction air quantity measuring apparatus for an engine provided with a valve overlap period during which an intake valve and an exhaust valve both open, comprises: an intake air quantity sensing section to sense an intake air quantity of air drawn into an intake system of the engine; an intake manifold inside air quantity calculating section to calculate an intake manifold inside air quantity of air in an intake manifold of the engine, from the intake air quantity by performing a balance calculation to calculate a balance between an intake manifold inflow air quantity of air flowing into the intake manifold, and an intake manifold outflow air quantity of air flowing out of the intake manifold; a cylinder induction air quantity calculating section to calculate a cylinder induction air quantity of air inducted into a cylinder section of the engine in accordance with the intake manifold inside air quantity; an engine stop position determining section to detect an engine stop of the engine, and to determine whether an engine stop position of the engine is within the valve overlap period; and a manifold inside air quantity modifying section to set the intake manifold inside air quantity equal to an overlap stop mode final air quantity and thereby to cause the intake manifold air quantity calculating section to use the overlap stop mode final air quantity as an initial value of the intake manifold inside air quantity in a next start of the engine when the engine stop position is within the valve overlap period.
According to the present invention, an engine cylinder induction air quantity measuring process comprises: calculating an intake manifold inside air quantity, from a sensed intake air quantity of an engine, by performing a balance calculation to calculate a balance between an intake manifold inflow air quantity, and an intake manifold outflow air quantity, and calculating a cylinder induction air quantity from the intake manifold inside air quantity; determining whether an engine stop position of the engine is within a valve overlap period; and modifying the manifold inside air quantity, by setting the manifold inside air quantity equal to an overlap stop mode final air quantity when the engine stop position is within the valve overlap period.